Nikkei cites unnamed sources saying that Apple in June asked its two main manufacturing partners, Foxconn and Pegatron, to study the costs of moving manufacturing of Apple products to the U.S. From the story:

“Apple asked both Foxconn and Pegatron, the two iPhone assemblers, in June to look into making iPhones in the U.S.,” a source said. “Foxconn complied, while Pegatron declined to formulate such a plan due to cost concerns.”

One source told Nikkei that moving production to the U.S. would double the current $225 cost to Apple of making an iPhone 7. Foxconn has a sales and service office in Brea, California, but no manufacturing facilities.